Every household in the UK is to have pornography blocked by their internet provider unless they choose to receive it, David Cameron is to announce.

In addition, Mr Cameron will say possessing online pornography depicting rape will be illegal, bringing England and Wales in line with Scotland. In a speech, the prime minister will warn that access to online pornography is "corroding childhood".

The new measures will apply to both existing and new customers.

Family-friendly filters will be automatically selected for all new customers - though they can choose to switch them off. And millions of existing computer users will be contacted by their internet providers and told they must decide whether to activate "family friendly filters" to restrict adult material. Customers who do not click on either option - accepting or declining - will have filters activated by default, Tory MP Claire Perry, Mr Cameron's adviser on the sexualisation and commercialisation of childhood, told the BBC.

Other measures expected to be announced by the prime minister include:

New laws so videos streamed online in the UK will be subject to the same restrictions as those sold in shops

Search engines will be given until October to introduce further measures to block illegal content. They have a "moral duty" to block illegal content, Mr Cameron will say

He will also call for warning pages to pop up with helpline numbers when people try to search for illegal content

Experts from the Child Exploitation and Online Protection Centre will be given more powers to examine secretive file-sharing networks

A secure database of banned child porn images gathered by police across the country will be used to trace illegal content and the paedophiles viewing it

Mr Cameron will say: "I want to talk about the internet, the impact it is having on the innocence of our children, how online pornography is corroding childhood. "And how, in the darkest corners of the internet, there are things going on that are a direct danger to our children, and that must be stamped out.

On Sunday, Mr Cameron called on internet companies to do more to block access to material depicting abuse

"I'm not making this speech because I want to moralise or scaremonger, but because I feel profoundly as a politician, and as a father, that the time for action has come. This is, quite simply, about how we protect our children and their innocence."

But former Child Exploitation and Online Protection Centre boss Jim Gamble told BBC Radio 4's Today programme it was important to "get to the root cause" of illegal pornography, by catching those responsible for creating it.

He added: "You need a real deterrent, not a pop-up that paedophiles will laugh at."But Ms Perry argued filters would make a difference, saying that the killers of schoolgirls April Jones and Tia Sharp had accessed legal pornography before moving on to images of child abuse. She added: "It's impossible to buy this material in a sex shop... but it's possible to have it served up on a computer every day."

In his speech, Mr Cameron will say that possession of online pornography depicting rape will be made illegal.

Existing legislation only covers publication of pornographic portrayals of rape, as opposed to possession. "Possession of such material is already an offence in Scotland but because of a loophole in the Criminal Justice and Immigration Act 2008, it is not an offence south of the border," he is to say.

"Well I can tell you today we are changing that. We are closing the loophole - making it a criminal offence to possess internet pornography that depicts rape." The move has been welcomed by women's groups and academics who had campaigned to have "rape porn" banned.Holly Dustin, director of the End Violence Against Women Coalition, said the group was "delighted"."The coalition government has pledged to prevent abuse of women and girls, so tackling a culture that glorifies abuse is critical for achieving this," she said."The next step is working with experts to ensure careful drafting of the law and proper resourcing to ensure the law is enforced fully."

'No safe place'

Mr Cameron, who has faced criticism from Labour over cuts to Child Exploitation and Online Protection Centre's funding, will insist that the centre's experts and police will be given the powers needed to keep pace with technological changes on the internet.

"Let me be clear to any offender who might think otherwise: there is no such thing as a safe place on the internet to access child abuse material," he will say.

A spokesman for Google said: "We have a zero tolerance attitude to child sexual abuse imagery. Whenever we discover it, we respond quickly to remove and report it. "We recently donated $5m (£3.3m) to help combat this problem and are committed to continuing the dialogue with the government on these issues." According to some experts, "default on" can create a dangerous sense of complacency, says BBC technology correspondent Rory Cellan-Jones. He says ISPs would dispute Mr Cameron's interpretation of the new measures - they are insisting they do not want to be seen as censors.What we will get, he says, is what ISPs call "active choice".

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Good luck telling your wife that you are going ask your service provider to unlock it!